Now, to a major public health issue in america, the flu. It is spreading like crazy this season. New numbers from the centers for disease control shows that 41 states is showing widespread outbreak. That's up from two weeks ago. Dr. Jennifer ashton is here to tell us about that. Good morning, guys. I think you need to go home after you're finished with the show, bianna. We don answers. We don't know why the flu this year is so bad. We don't know how bad it will get. What we do know is that the cases of influenza or flu-like illness are picking up speed. They're gaining momentum. We do expect them to get worse before it gets better. And these are particularly bad strains this year, making people incredibly sick. Even people who have had flu shots? Yeah. Listen, the flu vaccine is not 100% effective. It varies between 60% to 85% effective. But people who are vaccinated, if they do come down with influenza, seem to have a let severe course of the illness and a shorter course of the illness. It's not too late to get vaccinated. If you can see your doctor and get that vaccine today, it may save your life or someone else's life. Such an important note. Before we go, you were pointing out to me before the broadcast, that these new numbers out this morning are not even telling the full story most likely. That's right, dan. There's a lag time when patients go to a health care provider and when the cases get reported to the cdc and when the cdc releases the numbers. It varies about one to two weeks. We're not even close to through the worst part of it. One important tip, stay home if you're sick. If you're sick and not gotten the vaccine to protect yourself and you're ill, protect others and stay home from work or school. You need to go home. She says she doesn't have the flu. We'll see about that.

This transcript has been automatically generated and may not be 100% accurate.

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